A new study has found that social bees use chemical signals to warn other bees (belonging to the same species) about the presence of a nearby predator.

Researchers at the University of Tours (France) and the Experimental Station of Arid Zones of Almeria (EEZA-CSIC) have found that social bees use chemical signals to mark the flowers where they have been previously attacked. This way the bees leave a warning for other bees once they detect the presence of a predator.

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"Evasive alarm pheromones provoke an escape response in insects that visit a particular flower and until now, we were not sure of the role that these pheromones played in social bees," lead author of the study Ana L. Llandres, from the University of Tours, explained to Scientific Information and News Service (SINC).

"Our results indicate that, unlike solitary bees, social bees use this type of alert system on flowers to warn their conspecifics of the presence of a nearby predator," she said.

For their study, the research team carried out an experiment with solitary as well as social bees from different countries - Australia, China, Spain and Singapore. They created a simulation of predator attack by trapping the bees with pincers in some plants. They also used control plants where no predator attack took place.

They observed that the solitary bees responded in the same manner both in the case of flowers attacked by predators and with control flowers where no attack happened. But, social bees responded differently when approaching the flowers. Researchers noticed that the probability of social bees landing on control flowers was higher as compared to a flower where a conspecific (bees of same species) has been recently attacked and they have left a warning. This shows that the probability of social bees rejecting the flowers is much higher if the flowers had been previously attacked by predators.

The new study supports the idea that sociability of bees is linked to the evolution of warning signals.

The findings of the study are published in the journal Animal Behaviour.